JPS62145655A - Sealed lead storage battery - Google Patents

Abstract

PURPOSE:To provide a hermetically-sealed lead storage battery having a very long life and a high capacity and safe against thermal runaway, by using a negative electrode plate having 0.01% or more by weight of lignin and 0.001-0.15% by weight of barium sulfate in the active material of the negative electrode. CONSTITUTION:The negative electrode active material of a sealed lead storage battery contains at least 0.01%, preferably 0.1-0.4%, by weight of lignin, and 0.001-0.2%, preferably 0.01-0.1%, by weight of barium sulfate. Since there is a clear difference between the effect of 0.1% by weight of the barium sulfate and that of 0.2% by weight thereof, the maximum amount of the barium sulfate should be about 0.15% by weight. To maximize the performance of the battery, the negative electrode lattice thereof should contain substantially no antimony. If the lattice contained antimony, the charge-end voltage of the battery would be lowered to decrease the charging efficiency thereof.

Description

[Detailed description of the invention] 11. The present invention relates to a sealed lead-acid battery that is incorporated into portable electrical equipment and used in a cycle mode, or used as an emergency power source in a float mode or a trickle mode. It is.

In the sealed lead-acid battery, the oxygen gas generated at the positive electrode at the end of charging is Pb+-Q, 2→pb.

React with the negative electrode active material according to the formula, and P bo + H2SO4- + P b SOa + H20
P b S 04 + 2 e→P b + S 04
By returning to the original state again in the second method, the oxygen gas is processed in a closed system, making use of a so-called oxygen cycle, which seals the system.

That is, in order for this reaction to occur normally, it is necessary that PbSO4 always be present in the negative electrode active material, and if PbSO4 is not present, hydrogen gas will be generated from the negative electrode.

However, even if Pb5Oa exists in the negative electrode active material,
It is unavoidable that hydrogen gas is generated during large current charging or self-discharge, and the absorption of hydrogen gas at the positive electrode is extremely small compared to the absorption of oxygen gas at the negative electrode. The battery is equipped with a safety valve to release it to the outside and keep the battery safe. Note that this safety valve also serves to prevent oxygen gas from entering the closed system, and therefore has the structure of a check valve.

In addition, in this type of battery, in order to facilitate the movement of oxygen gas from the positive electrode to the negative electrode, the electrolyte must be gelled to ensure a gap for the oxygen gas to move, or the electrolyte must be able to absorb a large amount of the electrolyte. A strong porous body is placed between the positive and negative electrode plates, and the amount of electrolyte injected is limited to form voids in the coarse pores within the porous body to allow the movement of oxygen gas. ing.

However, the conventional sealed lead-acid battery configured as described above has a drawback that, if deep discharge is repeated, the battery life ends in a relatively short period of 50 to 200 cycles. The cause of this is thought to be at least one of stratification of the electrolytic solution caused by repeated charging and discharging, and local concentration of the oxygen gas absorption reaction. In any case, the cause of this short life is not due to softening of the positive electrode active material or corrosion of the positive electrode lattice, but rather due to the negative electrode active material partially becoming PbSO4.
Moreover, the so-called negative electrode sulfation, which accumulates without being reduced, is the root cause. Due to this sulfation of the negative electrode, charging efficiency decreases, and the voltage after charging also decreases.

In addition, although the above-mentioned phenomenon in conventional batteries of this kind is particularly noticeable when used in a deep discharge state, even when used in a constant voltage charging state such as a float method or a trickle method, the phenomenon due to the charging efficiency of the negative electrode It is observed that sulfation causes local current concentration at the positive electrode, which causes local corrosion of the positive electrode grid to progress and end its life. Furthermore, batteries used in this manner have the risk of thermal runaway due to a drop in voltage after charging, depending on the conditions of use.

In other words, in conventional sealed lead-acid batteries, not only the cycle method but also the float method and trickle method
The lifetime performance was insufficient for a highly reliable power source, and the main cause of this was partial sulfation due to a decrease in the charging efficiency of the negative electrode active material.

By the way, G~ used in conventional sealed lead acid batteries.
The negative electrode plate used in this study used the same active material composition as the negative electrode plate used in conventional open lead-acid batteries. That is, the negative electrode active material of this electrode plate contains 0.00% lignin in order to maintain its porosity and particularly improve low-temperature high-rate discharge characteristics. Barium sulfate is added in an amount of 1 to 0.8% by weight, and in order to maintain the porosity of the negative electrode active material so that it can be charged and discharged, and to prolong the duration of high rate discharge.
Carbon was added at ~2.5% by weight, and 0.6% by weight was added to further lower the charging voltage and improve charge acceptance.
In order to prevent the active material from falling off during assembly, organic short fibers have been added in an amount of about 0.2% by weight or less.

The present invention uses a negative electrode plate that does not reduce charging efficiency and does not cause sulfation in a sealed lead-acid battery.
To provide a long-life sealed lead-acid battery that solves the above-mentioned problems and can fully meet the demands of cycle, float, or trickle type applications that require high reliability. It is something that is born with the purpose of doing so.

The first aspect of the invention is a sealed lead-acid battery in which the negative electrode active material contains 0.01% by weight or more of lignin, and 0.00% by weight or more of lignin.
This method is characterized by the use of a negative electrode plate that contains barium sulfate in an extremely small amount of 1 to 0.15% by weight compared to conventional methods.

Further, as an embodiment of the present invention, a negative electrode plate further containing at least one of carbon, short organic fibers, and short lead fibers is used as the negative electrode active material, and the negative electrode plate is substantially Those characterized by having a lattice that does not contain antimony, and O11 as a negative electrode active material.
~0.4ffiffi% lignin, and ~0.01
We propose a device characterized by using a negative electrode plate containing 0.1% by weight of barium sulfate.

Furthermore, according to the present invention, since the negative electrode plate is less susceptible to sulfation, the specific gravity is higher than that of the dilute sulfuric acid electrolyte used in conventional sealed lead-acid batteries, for example, 1.29 to 1.35.
The present invention can be used as a sealed lead-acid battery that can use an electrolyte having a specific gravity of d, thereby providing a sealed lead-acid battery with high capacity and less risk of thermal runaway.

cusp The experiments that led to the present invention will be explained below.

Taking lignin and barium sulfate as additives to the negative electrode active material, we prepared a paste of the negative electrode active material by varying the amounts added, and applied this to a lattice made of a Pb-Ca alloy according to a conventional method. By curing, chemical conversion, and drying, 24 types of negative electrode plates were obtained. These three negative electrode plates and two positive electrode plates using a conventionally used PbCa-3n alloy for the lattice are laminated with a separator formed into a sheet mainly made of glass fibers with a fiber diameter of 1 μm or less. and obtained a polar group. The electrode group was inserted into the battery case, and then the battery case lid was adhered. Specific gravity 1 containing 1% by weight of silicic acid fine powder
．． A 30 d dilute sulfuric acid electrolyte was injected and a safety valve was installed to obtain a sealed lead acid battery.

Twenty-four types of sealed lead-acid batteries obtained in this way were subjected to an alternating charge and discharge test using a constant current, with one cycle of discharging to 80% of the nominal capacity and charging to 125% of the discharged electricity amount.
The results shown in Table 1 were obtained.

In addition, in order to compare with the test results of these sealed lead-acid batteries, one negative electrode plate of the 24 types mentioned above and two positive electrode plates with a large excess capacity were combined via a flat separator.
After inserting this into a battery case, we fabricated an open lead-acid battery in which a dilute sulfuric acid electrolyte with a specific gravity of 1.33 d was injected in excess so that there was enough liquid to flow, and for these, 40% of the theoretical capacity of the negative electrode was created. discharge, charge 125% of the amount of discharged electricity to 1
Table 1 also shows the results of the alternating charge/discharge test as a cycle.

From the results in Table 1, it can be clearly understood that lignin and barium sulfate are necessary for prolonging the life of the negative electrode in both sealed lead-acid batteries and open lead-acid batteries. The effects of these two additives are completely different.For open lead-acid batteries, the absolute amount of barium sulfate is more important than the presence of lignin, and at least 0.2% by weight is required. Even if the amount of lignin is less than 0.8% by weight, the negative electrode plate will still lose its porosity and its life will come to an early end.

In sealed lead-acid batteries, lignin is indispensable even at 0.01% by weight as shown in Table 1, but barium sulfate has a short lifespan at 0% by weight;
It suffices if it is present even in % by weight, and 0.001 to 0.1 % by weight is optimal, and if it exceeds 0.2 % by weight, the life will be shortened. Thus, in a sealed lead-acid battery, the negative active material contains at least 0.01% by weight, more preferably 0.01% by weight.
It is preferable that it contains 1 to 0.4% by weight of lignin and 0.001 to 0.2% by weight, more preferably 0.01 to 0.1% by weight of barium sulfate. Regarding barium sulfate, the addition amount is 0.1% by weight, and the addition amount is 0.2% by weight.
Since there is a clear difference in the amount of addition of
Its maximum addition amount should be around 0.15% by weight.

When barium sulfate is added in excess of 0.2% by weight, sealed lead-acid batteries undergo partial sulfation, resulting in a shortened lifespan. This means that it is essentially different from that of a lead-acid battery, in which oxygen gas absorption at the negative electrode plays an extremely important role. In other words, the fact that the negative electrode active material absorbs oxygen gas means that even when the battery is being charged, the active material particles that participate in this absorption reaction undergo a pb←-PbSO4 reaction, that is, are repeatedly charged and discharged, and are There is a possibility that PbSO4 remains unreduced at the final stage, and as the reduction efficiency to pbso4-pb decreases, the generated PbSO4 accumulates, so to prevent this, always use the same active material. It must be ensured that particles do not take part in this absorption reaction.

By the way, it is well known that barium sulfate in the negative electrode active material becomes the nucleus of Pb5Oa formation in A-shaped lead acid batteries, but it is thought that it can also become the nucleus of Pb5Oa in the absorption of oxygen gas in sealed lead acid batteries. It will be done. Therefore, dispersing barium sulfate as much as possible is one of the effective means for preventing short life due to Pb5Oa formation-M product-sulfation in sealed lead acid batteries. By the way, in sealed lead-acid batteries, as mentioned earlier, PBSO remains in the negative electrode active material even at the end of charging, so barium sulfate is not always actively added to serve as the nucleus of PBSOa generated during discharge. It is thought that it is not necessary. As described above, the present invention is based on the point of minimizing the addition of barium sulfate to a sealed lead-acid battery.

From the results in Table 1, the amount added is 0.01i
% lignin and 0.001-0615% barium sulfate are found to be suitable. In Table 1, the sealed lead-acid batteries whose symbols are in parentheses are the sealed lead-acid batteries according to the present invention.

The sealed lead-acid battery according to the present invention maintains a relatively high charging voltage until the end of its life, and is characterized by being less likely to have a "bump" in its charging curve. That is, the charging and discharging of the sealed lead-acid battery A according to the present invention and the conventional sealed lead-acid battery B in an alternate charging and discharging test using a constant current, where one cycle is discharging to 80% of the nominal capacity and charging to 125% of the amount of discharged electricity. Figure 1 shows the relationship between O, IOA charging voltage and capacity with respect to the number of times, and a sealed lead-acid battery according to the present invention that is new A'', a battery that is at the end of its life A'', and a conventional sealed lead-acid battery that is new As is clear from Figure 2, which shows the relationship between battery voltage during ICA charging and battery voltage during ICA charging, the charging voltage of conventional sealed lead-acid battery B is several tens of cycles. So 2.50
V/cell. As shown in the curve B'' of a conventional sealed lead-acid battery at the end of its life in Figure 2, it once rose to 2.7 to 2.8 V/cell, and then
2.4 of the "bump" created in this way.
The rapid rise point from around 0V to around 2.70V has the characteristic that it gradually becomes faster as the cycle repeats. ), even though conventional sealed lead-acid batteries start up at around 100% charge rate when new, the charge rate gradually decreases as the cycle is repeated, reaching around 90% at the end of their life. In other words, this indicates that the charging efficiency is decreasing with repeated cycles, and furthermore, the end-of-charge voltage of conventional sealed lead-acid batteries at the end of their lifespan "B" is decreasing. In actual use, this phenomenon not only causes an increase in float current and overcharge current, which accelerates corrosion of the positive electrode grid and shortens its lifespan.
Depending on the operating temperature and set voltage, there is a danger that thermal runaway may occur.

On the other hand, the sealed lead-acid battery according to the present invention, as shown in FIGS. 1 and 2, has the property that the voltage at the end of charging does not decrease, and furthermore, it does not form a "bump" until the end of its life. Furthermore, the rise of the uncharged voltage is always around 100% charging rate, and the charging efficiency does not decrease, so there is no risk of corrosion of the positive electrode grid or thermal runaway.

In the sealed lead-acid battery of the present invention, as an additive in the negative active material, for example, carbon, short organic fibers, short lead fibers are used as necessary for the same purposes as in conventional open-type lead-acid batteries. be able to. However, when carbon is used in open lead-acid batteries, no effect can be expected. Furthermore, in order to improve the electrical conductivity between the active material particles and the negative electrode grid, it is effective to add short fibers of lead, more preferably pure lead. From the viewpoint of workability in preparing and applying the paste, it is optimal that the short lead fibers have a fiber diameter of 10 to 200 .mu.m and a length of 2 to 15 mm.

Furthermore, since the sealed lead-acid battery used in the present invention has the characteristic that charging efficiency does not easily decrease, it is possible to use an electrolyte with a higher specific gravity than conventional batteries, which increases the capacity accordingly. be able to. Conventional sealed lead-acid batteries used dilute sulfuric acid of about 1.26 to 1.32 d,
If the same life performance is acceptable, the sealed lead-acid battery according to the present invention can use dilute sulfuric acid, which has a specific gravity of 1.29 to 1.35 d, which is about 30 points higher, so the capacity can be increased by more than 10% with the same volume. be able to.

In the sealed lead-acid battery of the present invention, in order to maximize its effects, the negative electrode grid must substantially not contain antimony. In other words, if antimony were contained, it would lower the voltage at the end of charging and reduce the charging efficiency.

Since the sealed lead-acid battery according to the present invention does not reduce its charging efficiency and therefore does not undergo sulfation,
It has an extremely long life not only for cycle use but also for float and trickle use, and is a product with high capacity and safe against thermal runaway.

As described above, the present invention provides a sealed lead-acid battery that can fully meet applications requiring high reliability.
It has extremely high industrial value.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between O, ICA charging voltage and capacity with respect to the number of charging and discharging times in an alternate charging and discharging test of a sealed lead acid battery A according to the present invention and a conventional sealed lead acid battery B. Figure 2 shows a new sealed lead-acid battery A" according to the present invention.
2 is a graph showing the relationship between the battery voltage during 0 and ICA charging with respect to the charge amount for conventional sealed lead-acid batteries A'', which are at the end of their lifespan, and B'', which are new and conventional sealed lead-acid batteries, and B'', which is at the end of their lifespan.

Claims (1)

[Scope of Claims] 1) A sealed lead-acid battery characterized in that a negative electrode plate containing 0.01% by weight or more of lignin and 0.001 to 0.15% by weight of barium sulfate as a negative electrode active material is used. . 2) The sealed lead-acid battery according to claim 1, further comprising a negative electrode plate containing at least one of carbon, short organic fibers, and short lead fibers as a negative electrode active material. 3) A sealed lead-acid battery according to claim 1, characterized in that the negative electrode plate is provided with a grid substantially free of antimony. 4) Claim 1, characterized in that a negative electrode plate containing 0.1 to 0.4% by weight of lignin and 0.01 to 0.1% by weight of barium sulfate as the negative electrode active material is used. Sealed lead-acid batteries as described in .